Seam and method of making the same



P" 1947- K. A. STRITTER SEAM AND METHOD OF MAKING THE SAME Filed May 26, 1943 Fig: 3

Fig.4

' Fig5 //vv NTUR MQ Search Roon Patented Apr. 1, 1947 UNITED STATES PATENT OFFICE SEAM AND METHOD OF MAKING THE SAME Karl A. Stritter, Nahant, Mass., assignor to United Shoe Machinery Corporation, Fleming- 11 Claims.

This invention relates to improvements in seams and to improved methods of making seams primarily intended for use in uniting relatively heavy pieces of work such as those employed for shoe soles, in which the substance of the work is more or less compressible and the thickness several times greater than the diameter of the thread employed in the seam as distinguished from cloth sewing in which the thickness of the work is comparatively negligible. Although not so restricted in its application the invention is herein illustrated with particular reference to the attachment of outsoles to shoes.

It has been proposed to secure together two or more layers of sheet material by means of a fairstitch seam, the stitch loops of which extend through the layers and are enlarged or flattened at their closed ends so that the enlargements tend to hold the seam in place. Such an expedient, however, cannot be relied upon to hold the layers securely united if they are subjected to any substantial strain tending to separate them inasmuch as the enlarged or flattened ends of the stitch loops offer no very substantial resistance to withdrawal of the loops from the stitch holes, the remaining portions of thread in the loops still retaining their full flexibility.

One object of the present invention is to provide for positively locking the stitch loops of a fairstitch seam sewn through a plurality of layers of stock thereby to insure that the layers will be securely and permanently united by the seam.

With this object in view the invention, considered in one of its aspects, provides an improved method of uniting pieces of stock which, as herein exemplified, comprises sewing a fairstitch seam through a plurality of layers of stock with a thread composed, at least in part, of plastic fibers such as the synthetic fiber-forming polymeric amide known as nylon (the sewing being effected so as to leave the closed ends of the stitch loops protruding at one side of the layers), softening the plastic in the protruding end portions of the stitch loops, and pressing the softened portions against the exposed surface of the adjacent layer of stock and allowing them to harden thereby forming locking heads from bonded fibers composing the thread at the closed ends or blghts of the stitch loops for positively holding the loops in place. Advantageously the thread may consist entirely of nylon fibers and the closed ends of the stitch loops may be softened and headed over upon the adjacent surface of the stock by the passage of the stock over a heated Work supporting surface during the progress of the sewing operations, the work being pressed toward the work support to effect the flattening of the headed portions. Preferably, but not necessarily, the thread is provided with a coating of an unsolidified cementitious or resinous substance such, for example, as a phenolic resin, in a liquid or semiliquid form, which becomes solidified after the stitches have been formed and which, by bonding the stitch loops to the walls of the stitch holes in the layers of stock, provides additional insurance against dislodgement of the stitches. When such a coating is used, however, the resulting seam is less flexible than when the thread is uncoated.

As herein illustrated with reference to the attachment of an outsole to a shoe, my invention involves laying an outsole upon the bottom of a welted shoe, presenting the shoe to a fairstitch sewing machine supplied with nylon thread and equipped with a heated work support and a cooperating presser foot, and operating the machine to sew a fairstitch seam with said thread through the extension edge portions of the welt and the outsole and to leave the closed ends of the stitch loops projecting somewhat at the tread side of the outsole where they will be softened in passing over the heated work support and flattened or headed over against the outsole. Thereafter the softened loop ends will be permitted to cool and set so as positively to lock the loops or stitches in place and insure that the outsole will be securely attached to the welt. Thus, the loops will be locked in place as a result of two separate actions, namely, the ad hesion of the plastic fibers to the stock and the formation of enlarged solid heads on the loops by bonding the fibers together cohesively in the manner of autogenic welding. Preferably, a channel is provided in the tread side of the outsole to receive the stitches and a channel flap, formed by the operation of cutting the channel, is laid over the flattened ends of the stitch loops to cover them and protect them from wear. In its application to the attachment of outsoles the invention is not limited, however, to the manufacture of welt shoes, it being useful also in making shoes of other types, for example, McKay sewed shoes and shoes in which the outsole is stitched to a middle sole instead of a welt. The invention is also useful for the purpose of securing together layers of shoe upper materials or other shoe parts or, in general, to methods of uniting pieces of stock or sheet material in the manufacture of articles of various sorts. Moreover, my improved method is not limited in its application to the uniting of layers of material but is capable of providing for locking in place the stitches of a seam sewn, for decorative or other purposes, in a single ply of material.

The invention will now be explained in detail with reference to the accompanying drawings, in which Fig. 1 is a perspective view of the toe portion of a welt shoe the outsole of which has been attached in accordance with my improved method, portions of the outsole and the welt having been broken away to show how the closed ends of the stitch loops are locked at the tread side of the outsole;

Fig. 2 is a perspective view of the toe portion of the shoe showing the bottom or tread side of the outsole and illustrating the appearance of the shoe after the protruding ends of the stitch loops have been softened and flattened but before the channel flap has been laid;

Figs. 3 and 4 are views illustrating the attachment of the outsole to the welt by the use of a fairstitch sewing machine, Fig. 3 showing the outsole and the welt in vertical section along the line of the seam being sewn by the machine and showing certain of the operating instrumentalities of the machine in front elevation, and Fig. 4 showing the operating instrumentalities in side elevation and showing in cross-section the portion of the shoe being operated upon; and

Fig. 5 is a vertical sectional view, on an enlarged scale, of the welt and the outsole of the shoe, the section being taken along the line of the seam and illustrating how the stitches are locked in place.

My improved method of uniting pieces of stock is illustrated by the drawings in its application to the attachment of an outsole 8 to a shoe of commercial Goodyear welt construction, the shoe, as shown in Fig. 4, comprising an insole I0 having a marginal sewing rib l2, an upper l4 and a welt l6 which are secured to the insole rib by inseam stitches I8, and the usual filler 20 for the bottom cavity bounded by the sewing rib. The outsole 8 is laid, rough rounded and channeled in the usual manner, the channeling operation providing a marginal stitch-receiving channel 22 at the tread side of the sole and forming a channel flap 24 which is subsequently raised to open the channel and left in a raised position, as indicated in Fig. 2. Having been thus prepared, the outsole is ready to have its margin attached to the welt and as herein illustrated this operation may advantageously be performed by the use of a fairstitch sewing machine of the type disclosed, for example, in United States Letters Patent No. 645,424, granted March 13, 1900, upon application of Edwin F. Mower. Portions of such a machine are shown in Figs. 3 and 4 of the drawings, the throat plate or work support bein indicated at 26. the presser foot at 28, the awl at 30, the hooked needle at 32. the thread carrier at 34, the loop placer at 36, and the thread retainer at 38. During the operation of the machine the extension edge portions of the welt and the outsole are supported and compressed somewhat between the work table and the presser foot at the sewing point and they are fed step by step as the successive stitch-forming operations are being performed. The awl. the needle, and the other operating instrumentalities cooperate to cause the thread 40, leading from a source of supply, not shown, to be drawn downwardly through the welt and the outsole in the form of a long loop, as indicated at 42 in Fig. 3; to cause the loop to be drawn upwardly until its bight is left projecting only a small amount at the tread side of the outsole, as indicated at 44; and finally to cause the pro- J'ecting bight portion of the loop to be flattened against the outsole by means of the work support 26, as indicated at 46. Thus, during continued operation of the machine, a serially connected line of loops is formed. For an understanding of further particulars in regard to the construction and mode of operation of the machine, reference may be had to the above-identified patent.

As has been indicated above, an object of the invention is to provide an improved method of inserting a novel seam, primarily in such heavy substances as leather shoe outsoles or insoles in which the stock is compressible and of substantially greater thickness than the diameter of the thread. The nature of a thread seam in such substances differs materially from that employed in relatively thin textiles because the lengths of thread embedded in the stock are firmly gripped by the stock in a manner not experienced with cloth sewing. Also, problems of abrasion between the stock and thread and flexibility of the finished seam are widely different from those in textile sewing.

In using the above-described machine for securing an outsole to a shoe, in accordance with my improved method as herein illustrated, the machine is supplied with a thread composed, either wholly or in part, of solidified thermoplastic material (thread composed of twisted strands or fibers of nylon having been found suitable for this purpose) and the portion of the work support which functions to flatten the projecting end or bight portions of the stitch loops against the outsole is heated, as by means of an electric heating unit 48 (Fig. 3), to insure that the end portions of the loops will be in a soft and pliable condition while being subjected to pressure. Advantageously, also, the presser foot 28 may be formed with an extension 50 for acting in conjunction with the heated work support to insure that the ends of the stitch loops will be effectively headed over, flattened and solidified against the work.

In the several figures of the drawings the loops of the completed fairstitch seam are indicated at 52. In the sewing of the seam, as the feeding of the work advances the projecting ends of the stitch loops across the flat upper surface of the heated portion of the work support 26, the thermoplastic substance of which the loop ends are composed is softened by the heat and resolved into a plastic mass integral with the plastic fibers of the rest of the thread 40 by bonding the fibers autogenically. The softened end portions of the stitch loops 52 are consolidated, compressed and flattened against the channeled surface of the outsole by the ironing action of the heated work support under the compression of the outsole by the presser foot with the result that solid flat heads 54 are formed at the lower ends of the stitch loops, the heads extending outwardly beyond the ed e of the stitch holes, and these heads 54 quickly cool and become hardened or set as they are moved away from the heated work support by the continued feeding of the work. The heads 54 overlap the lower surface of the outsole, and after they have become hardened they function as looking members positively to hold or look the individual stitch loops in place ooamfl noon in the outsole while the thread between stitches remains unaffected. It is to be understood, however, that the closed ends of the stitch loops are also held in place in the stitch holes by means of the latent adhesive property of the nylon thread which causes the softened end portions of the stitch loops to adhere strongly to the outsole as they are allowed to harden. Consequently, even if the loop ends are not flattened or even enlarged or headed over so as to overlap the lower face of the sole to any substantial extent, they will nevertheless be held in place by the adhesive bonding action of the softened plastic at the tread side of the sole. Normally, of course, the locking of the stitch loops will be effected as the joint result of the heading over of the ends of the loops including the cohesive bonding action of the material in the fibers and the adhesive bond which is established between the 'loop ends and the adjacent portions of the outsole material. After the sewing of the seam and the heading over of the projecting end portions of the stitch loops have been completed the channel flap 24 is laid in the usual manner and serves to cover the locking heads 54 and protect them from wear. The heads 54 being flat and substantially flush with the bottom surface 22 will not produce ridges or protuberances in the channel flap and consequently there will be no necessity of forming the usual groove in the channel for the purpose of receiving the stitches.

In order to provide still further insurance that the stitch loops 52 will be locked in place in the welt and the outsole, it is preferred to coat the thread 40 with a plastic substance before the seam is sewn, the plastic substance being in a soft or semifluid state so that it will serve to lubricate the thread and having also adhesive properties while soft so that the stitch loops will be adhesively secured thereby to the walls of the stitch holes. The coatin operation may be accomplished by passin the thread 40 through a cement pot 56 (Fig. 3) containing a phenolic resin in a liquid or semiliquid form. During the sewing of the seam the soft resin will lubricate the thread in substantially the same manner as the wax which is customarily employed and, after the seam has been completed, the resin will harden and will effectively bond the loops 52 to the walls of the stitch holes throughout the full thioknss of the outsole and the welt. Thus the stitch loops will be securely held in place even after the shoe has been worn to such an extent that the channel flap 24 and the locking heads 54 on the stitch loops have become worn away.

The use of a single thread fairstitch'seam in the attach ng of an outsole to a shoe is particularly advantageous in that such a seam facilitates the flexing of the outsole, rendering it capable of bending freely with the foot since there are no strands connecting the stitch loops at the outer or tread side of the outsole to stiffen the soe and resist bending or flexing thereof. Al o, the withdrawn bights being entirely separated at one side of the work, the thread between stitches at the other side of the work will remain uncemented thereto, thus avoiding stiffness in the completed shoe. Moreover, this effect is enhanced when the thread is not coated, thus leaving the thread in the major portions of the stitch holes free and uncemented to the work. The locking effect of the solidified plastic heads formed at the closed ends of the stitch loops, with or without the additional locking effect produced by the use of the separate adhesive coating upon the thread constituting the seam, insures that the stitches of a fairstitch seam will be securely held in place in the work. This renders it practicable to employ such a seam in the attaching of an outsole to a shoe or in the securing together of layers of stock in the manufacture of articles or products of various sorts. The seam may be sewn by means of a fairstitch sewing machine of conventional construction modified only to the extent of providing the machine with means for coating the thread and for heating the projecting ends of the stitch loops.

It is to be understood, however, that my invention is not limited to the use of fairstitching as the means for uniting layers of stock since seams of other types may be employed as, for example, a chain stitch seam or a lock stitch seam. If a seam of either of the last-mentioned types is employed the portions of the stitches which extend through adjacent stitch holes in the work will be connected at both sides of the work instead of at one side only as in the case of fairstitching and in such instances the plastic in the connecting portions of the stitches at one side of the work will be softened after the stitches have been formed, and will thereafter be allowed to cool and harden to cause the plastic to adhere to the work to lock the scam in place. In case a lock stitch seam is to be employed for attaching an outsole to a shoe, the lower or needle thread only need be made wholly or in part of thermoplastic material as it is only the lower end portions of the stitch loops of this thread which are to be relied upon to form the locking heads for holding the stitch loops in place. It is to be noted that if such a lock stitch seam, or a chain stitch seam is employed, the portions of the stitches which connect the loops at the lower or tread side of the work will be softened and disintegrated by the heat applied thereto so that the connections between adjacent stitches will be broken at that side of the sole. Thus there will be no connections between the stitches at the tread side of the sole to stiffen the sole so as to resist bending or flexing thereof and the shoe bottom will be more flexible than in a shoe having a conventional look stitch or chain stitch seam attaching the outsole to the shoe.

The thread used for sewing the outsole attaching seam, or for sewing any seam in the practice of my improved method, may be composed of or contain a plastic which is not capable of being softened by heat. In such a case a suitable solvent may be employed to soften the portions of the stitches which are to be secured to the work by the formation of autogenic locking heads on the stitches or by the inherent adhesive and cohesive properties of the plastic constituting the thread. The solvent may be applied to the stitches, for example, by means of a roll arranged to dip into a pan containing the solvent and to extend through an opening in the "work support of the sewing machine in a locality to engage the stitches at the lower side of the work.

It is also within the scope of the invention to employ, for securing together one or more layers of stock, spaced fastenings other than stitches, for example, pegs or staples made at least in part of a plastic. In such a case, after the fastenings have been inserted in overlapped portions of the layers of stock, the end portions of the fastenings adjacent to one exposed surface of the overlapped layer portions will be softened and these end portions will become locked to the adjacent layer of stock as they are allowed to harden, the

locking being effected by the inherent adhesive properties of the fasteners themselves or by the forming of locking heads as by means of pressure applied to the softened portions of the fasteners, or by both such means.

Certain features of the invention herein disclosed are claimed in a divisional application for United States Letters Patent Serial No. 598,058, filed June '7, 1945.

Having described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. That improvement in methods of uniting pieces of heavy shoe sole stock which consists in sewing a line of stitches through a plurality of layers of stock with a thread of a diameter substantially less than the thickness of the stock, said thread being composed of a plastic having latent adhesive properties, acting progressively during the continuance of the sewing operation upon portions of the completed stitches at one side of said layers and in the order in which the stitches were formed to soften said portions of the stitches, and allowing said softened portions to harden to cause them to adhere to the adjacent layer of stock to lock the line of stitches in place while leaving the thread elsewhere within the stitches free of treatment.

2. That improvement in methods of uniting pieces of stock which consists in sewing a fairstitch seam through a plurality of layers of stock with a thread composed, at least in part, of thermoplastic material and leaving the closed ends of the stitch loops projecting at one side of said layers, heating the projecting portions of said loops thereby softening the thermoplastic material therein, pressing said portions against the exposed surface of the adjacent layer thereby causing them to extend outwardly beyond the edges of the stitch holes, and allowing the thermoplastic material in said portions to harden thereby forming locking heads at the ends of the stitch loops for anchoring the loops in said layers.

3. That improvement in methods of attaching outsoles to shoes which comprises laying an outsole upon the bottom of a welted shoe, sewing a fairstitch seam through the welt and the outsole with a thread composed, at least in part, of thermoplastic material and leaving the closed ends of the stitch loops projecting at the tread side of the outsole, heating and thereby softening the protruding loop ends, pressing the softened loop ends against the outsole thereby forming heads thereon extending outwardly beyond the edges of the stitch holes, and allowing said heads to cool and harden thereby to lock the seam in the outsole.

4. That improvement in methods of attaching outsoles to shoes which comprises laying upon the bottom of a welted shoe an outsole having in its tread side a marginal stitch-receiving channel and a channel flap, sewing a fairstitch seam through the welt and the outsole with a nylon thread and leaving the closed ends of the stitch loops protruding in said stitch channel, applying heat and pressure to said protruding loop ends thereby softening them and flattening them against the channeled portion of the outsole, allowing said flattened portions to cool and harden thereby to lock the loops in the outsole, and laying the channel flap to close said channel and cover the flattened portions of said loops.

5. That improvement in methods of attaching outsoles to shoes which comprises applying a coating of unsolidified cement to the thread of a fairstitch sewing machine as the thread is being drawn from the source of supply, feeding the extension edge portions of the welt and outsole of a welt shoe through the machine thereby sewing a fairstitch seam through the welt and the outsole with said thread while the coating remains unsolidified and leaving the loops of the stitches projecting at one side of said layers, applying heat to the projecting portions of said loops thereby softening them, flattening said softened portions against said side of the work, and allowing said coating to harden and the heated and softened portions of said loops to cool and set thereby causing the stitches to become locked in place by said coating and by the flattened portions of said loops.

6. That improvement in methods of attaching outsoles which consists in inserting spaced fastenings composed of a solidified plastic substance having latent adhesive properties through the outsole and another bottom member of a shoe, softening the end portions of said fastenings ad- J'acent to the tread side of the outsole coincidently with the insertion of successive fastenings, applying pressure to said softened portions thereby forming heads on said fastenings overlapping the adjacent outsole surface, and allowing said heads to harden to lock the outsole to the shoe.

7. A seam connecting heavy shoe sole stock of a thickness substantially greater than the diameter of the thread employed comprising a single continuous thread only of fibers consisting of a plastic and having throughout its length a series of loops extending entirely through the stock with the bight or closed end portions of the loops withdrawn from the stock and exposed in separated relation to each other, said loops being retained in the stock by means of locking heads composed of the plastic of said fibers autogenically bonded and solidified at the bight portions of the loops only.

8. A thread seam for heavy shoe sole stock of a thickness substantially greater than the diameter of the thread in the seam, said thread comprising a continuous strand composed of fibers of a solidified plastic hafi wsive erties and having throughout its eng li'a' series of loops extending through and being withdrawn from alined perforations in a plurality of layers of stock, said loops being secured in place in said erfora hea formed in separated relation to each other by autogenically bonding the fibers at the closed ends of the loops, said locking heads being larger in diameter than said perforations and separated from other loops, and each of said heads consisting of a solid mass integral with the fibers of said strand and secured to the outer surface of the adjacent layer of stock by the adhesive properties of said plastic.

9. That improvement in methods of sewing heavy shoe sole stock of a thickness substantially greater than the diameter of the thread employed which consists in inserting a line of stitchescomposed of loops of fibrous thread passing entirely through the stock operated upon, withdrawing the bight portions of the loops during insertion of the stitches, and treating progressively duringsewing operations the bight portions of said loops while separated from each other adjacent to one side of the stock, to bond said bight portions of thread to the stock while the other portions of thread in the loops remain untreated and free for movement relatively to the stock when flexed.

10. That improvement in methods of sewing heavy shoe sole stock of a thickness substantially greater than the diameter of the thread employed which consists in inserting a line of stitches composed of serially connected loops of fibrous thread, withdrawing successive bight portions of the loops from the stock during insertion of the stitches, treating the Withdrawn bight portions to provide an adhesive material between the thread and the stock, and causing the adhesive material to harden and to bond the bight portions only to the stock while the other portions of the thread in the loops remain untreated and free for movement relatively to the stock when flexed.

11. A shoe having an outsole of heavy stock attached by a seam comprising a continuous thread of a diameter substantially less than the thickness of said outsole stock, said thread being formed into loops extending entirely through the outsole with their bights exposed in separated relation at the surface of the outsole and comprising fiexible plastic fibers having latent adhesive and cohesive properties, the loops of which thread are retained in the outsole by means of the plastic in the fibers autogenically bonded to- 5 the stitches lie.

KARL A. STRITTER.

REFERENCES CITED The following references are of record in the 10 file of this patent:

UNITED STATES PATENTS Number Name Date 44,275 Blake Sept. 20, 1864 5 559,129 Goodu Apr. 28, 1896 1,368,059 Schick Feb. 8, 1921 1,370,797 Egerton Mar. 8, 1921 1,419,998 Valois June 20, 1922 1,891,412 Grune Dec. 20, 1932 20 2,048,343 Liebowitz July 21, 1936 2,314,098 McDonald Mar. 16, 1943 45368959 Schick Feb. 8, 1921 2,353,960 King July 18, 1944 645,424 Mower Mar. 13, 1900 25 

